Simplified methodology to evaluate the external sulfate attack in concrete structures

Abstract

The external sulfate attack is a degradation process that causes expansion and cracking in concrete structures. Due to the absence of simplified methodologies to predict the potential damage, codes specify that sulfate resistant cement should be used whenever the surrounding sulfate concentration surpasses a predefined limit. This may lead to penalizing measures as the size of the element or the mechanical properties of the concrete used are not considered. In the present work, an alternative approach is proposed. A simplified chemo-mechanical methodology is deducted to assess the potential damage in concrete elements exposed to sulfate rich environments. Equations to estimate the penetration of sulfates are derived from a numerical model taking into account sulfate consumption, acceleration of the penetration induced by cracking and decrease in diffusivity caused by pore filling. Failure modes associated to this phenomenon are analyzed and a set of equations to assess the risk of failure are deducted. Finally, a parametric study with different geometries of elements and surrounding sulfate contents is performed. The results show that the criterion included in codes might be modified depending on the characteristics of the structure.